The proposed study aims to increase our understanding of proteinase inhibitors at inflammatory sites and their role as regulators of macrophage function. Unlike circulating blood proteinases and proteinase inhibitors, our knowledge of proteinases and proteinase inhibitors at inflammatory sites is limited. In preliminary studies we detected two molecules which account for the bulk of proteinase inhibitory activity associated with inflammatory peritoneal macrophages. One was identified as Alpha1-proteinase inhibitor (Alpha1PI), also called Alpha1-antitrypsin; it is apparently not of macrophage origin, but is derived from circulating Alpha1PI and is present in high concentrations at inflammatory sites and binds to macrophages via an unknown mechanism. The second inhibitor, macrophage proteinase inhibitor (MPI), does not correspond to any previously described molecule and appears to be of macrophage origin. The goal of the proposed study is to characterize the macrophage-associated proteinase inhibitors MPI and Alpha1PI. The major focus will be on MPI. We will examine whether MPI is synthesized by peritoneal macrophages, alveolar macrophages, monocytes, and/or other cells. MPI will be purified to homogeneity and biophysical characteristics determined. We will examine which of several functionally important inflammatory proteinases are inhibited by MPI and whether MPI, like Alpha1PI, is inactivated by oxidants. An important section will investigate whether MPI production is altered by agents known to functionally alter macrophages, namely activating agents such as phorbol myristate acetate in vitro and BCG in vivo, and agents which suppress macrophage functions, namely glucocorticosteroids. Study of Alpha1PI will be limited to examining the nature of its binding to macrophages. The basic information on macrophage-associated proteinase inhibitors to be derived from this study will eventually be of benefit clinically for therapeutical manipulation of defense functions of macrophages.